Originally Posted by
tspoon
I've had similar problems, and am about to procure for myself this cheap form of insurance. Is your shifting indexed or friction. I use friction and took great care to adjust the stopping point of the derailleur, but found it would occasionally (very rarely, but non-0) jump over regardless. It might be the fact of changing up (down?) multiple gears in one movement, or it may be the tension adjustment for the derailleur causing it to not be in the most ideal place when in the largest rear cog. I'm not 100% sure whether that causes that problem or not, but it's a possibility I'm considering. Has anybody else experienced similar and solved the problem?
Mine in the photo above is indexed 8 speed. It is quite possible that the wider chain and wider cassette spacing with an 8 speed system makes it less likely that my chain will go past the big sprocket than a narrower chain. But that said, my road bike is 10 speed, that has never gone past the big sprocket into the spokes either, so maybe that has nothing to do with it.
I try to avoid shifting too many gears quickly to either end of the cassette. If I am shifting lots of gears quickly, I only do that in the middle of the cassette. A few years ago on my Lynskey I upshifted too fast and put the chain between my cassette and dropout where it jammed. And I had four panniers on the bike so it was not quick to loosen up the wheel and free the chain as I had to pull the luggage off of the bike first.
My rando bike drive train in the photo below, also 8 speed system, I built up that bike in 2016 but I built that wheel in 2004, the derailleur on that bike is from the 90s. And yes it was winter when I built up the bike, so that is why the photo shows the bike in snow.
I set the stop on the derailleur quite carefully to make sure that it won't go too far. Do that pretty much the way that ThermionicScott described it. And I do that on each chainring just to make sure that the position of the cage does not have anything to do with it under different chain tensions.
I am trying to remember how the tabs worked on the spoke protector, the bikes in the photos above are both 36 spoke wheels, they have three tabs that clip on to the hub flange and there are 12 spokes between each tab, but I think that the three tab version does not clip onto a 32 spoke wheel, so you need to get the spoke protector for the right number of spokes to get the tab to clip on right.
This reminds me that I still need to put one on my Lynskey. I keep forgetting.